# Flow over Weir

Introduction A weir is a gap within the sidewall of a tank at high. The stream of liquid popping out the weir is named a nappe, sheet or vein. There isn't a distinction between a notch and weir besides that the previous is a small construction and has sharp edges. A weir typically an overflow construction, with a broad crest, construct throughout an open channel. The phrases air and weirs are used synonymously normally. The highest of weir wall over which the liquid flows is named the sill or crest. The pinnacle underneath which the weir is discharging is measure from the crest to the free floor.
A weir or notch is usually used for measuring the circulate of liquids. On this experiment, we ar utilizing the oblong weir and triangle weir. Rectangular weir and triangular weir (v-notch) ore typically utilized in water provide, wastewater and sewage system. They consists of a pointy edge airplane with rectangular and triangular profile for the water circulate. Broad-crested weirs will be noticed in dam spillways the place the broad edge is beneath the water floor throughout your complete stream. Circulate measurement installations ith broad-crested weirs will meet accuracy requirement provided that they're calibrated. goal To find out the traits of open channel circulate over; * An oblong notch * A triangular (v-notch) * To find out values of the discharge coefficient for each notches Methodology Common options of the circulate will be decided by direct commentary. Discharge coefficient values will be decided from measurements of the peak of the free floor of water above the notch base and corresponding quantity circulate charge Tools To be able to full the experiment, we want plenty of items of apparatus * The F1-10 haudralics bench which permits us to measure circulate by timed quantity assortment * The F1-13 stilling baffle The F1-13 rectangular and Vee notch * Vernier Top Gauge (equipped with F1-13) * Stopwatch * Spiril stage four four 2 2 5 5 eight eight 7 7 6 6 three three 1 1 Determine 1: Circulate over Weirs - Determine 2: Circulate over Weirs - vee notch weir rectangular notch weir 1 1 5 5 2 2 6 6 Hydraulics BenchBasket of glass spheres three three Weir channelVolumetric measuring tank four four (V) Vee notch weir7 7 Rectangular weir Hook & level gauge Hook Gauge and Scale8 eight There are totally different shapes of weirs that can be utilized to measure the volumetric circulate charge. These shapes with their dimension are proven in fig three beneath. Determine three: Particulars of weirs
Technical Knowledge The next dimension from the tools are used within the acceptable calculation. If required these values could also be checked as a part of the experimental process and substitute with your individual measurements. * Width of rectangular notch, b= zero. 030 * Angle of vee notch, o=90 diploma Concept As a result of the depth of circulate above the bottom of notch is said to the amount circulate charge via it, the notch kinds a helpful circulate measurement system. The classical end result for circulate over notch are obtained by an software of the Bernoulli equation, from a degree effectively up stream to a degree simply above the notch. This method requires plenty of very substantial assumptions and it yields the next outcomes: For Rectangular Notch, the system is given by; Qt=Cd23b(2g)H32 For Vee-notch, the system is given by; Qt=Cd815tan(? 2)(2g)H52 The place; Qt= Quantity circulate charge H = peak above notch base B = width of rectangular notch ? = angle of the vee in triangular notch; Cd= the discharge coefficient, which needs to be decided by experiment These will be rearrange to present; Cd=3Qt2b2gH32 For rectangular notch Cd=15Qt8tan? 22gH52 Foe vee notch. Dialogue.
From the experiment, we're about to find out the discharge coefficient of the each rectangular and the triangular notches. The discharge coefficient for the oblong notch are affect by its H and likewise its volumetric circulate charge whereas the triangular notch are affect by its o, H and likewise its volumetric circulate charge. From the end result, we are able to see that the volumetric circulate charge of each notches are enhance. This confirmed present that the water outflow enhance because the H elevated. These is suppose to occurred as, the water stage enhance, the Water outflow from the notch enhance over the time.
However from discharged coefficient, we are able to see that the worth of each notches usually are not secure. This can be from the friction on the head of the notches in the course of the starter of experiment. The friction will have an effect on the time taken to gather 1liter of water for V-notch and 5 litre of water for the Rectangle notch. Thus it should impact the volumetric circulate charge and likewise the discharge coefficient because the volumetric circulate charge affect the worth of Cd. The intention of this experiment is to find out the worth of the discharge coefficient for each notches of rectangular notch and likewise triangular (V-notch).
The discharge coefficient values will be decide from the measurements of the peak of free floor of water above the notch base and corresponding quantity circulate charge For discharge coefficient of Rectangular Notch, the system is given by; Cd=3Qt2b2gH32 For discharge coefficient of V-notch, the system is given by; Cd=15Qt8tan? 22gH52 As compared, for rectangular notch, the theoretical worth of its discharge coefficient, Cd, is ------. Nevertheless, the experimental worth of Cd seems to be 2. 31. Primarily based on experiment that we performed, the proportion error for rectangular notch is--.
This is because of some errors that ccur throughout experiment. For instance parallax error. Nevertheless, for V-notch, the theoretical worth is ---, however theoretical worth is---. There's not a lot of a distinction between its theoretical worth and precise worth. This imply that the circulate is laminar, and never a lot vitality is loss via friction. The derivation of values are contributed by the error throughout handing the experiment, if we take it as general error, most of error occurred when step of taking the peak began. First, we now have to cautious concerning the peak of datum. For comfort, is is recommendation that to take your first datum as zero.
Aside from that, it is usually recommendation that th time must be taken three occasions in order that we are able to take the common in order that the error will be decrease. In addition to, The idea doesn't put vitality loss or viscosity of the water circulate into consideration, nevertheless it solely depends upon the circulate charge, the width of the notches and peak of the notches. Nevertheless, in actuality, water currents or circulate charge might not be fixed on a regular basis and it's troublesome to take care of the water stage peak above the notches as what he need. The cross part space over the weir with flowing water at decrease charges is small evaluate to excessive charges.
It is because at decrease circulate charges, the time for assortment of water varies quite a bit evaluate to increased circulate charges. It require an extended time to gather a certain quantity of water to measure the circulate charge at decrease circulate charge attributable to viscosity of water. Furthermore, vitality is conserved attributable to slower velocity of circulate of water. At increased circulate charges, water flowing might have already got the vitality to create a relentless water circulate. Whereas at a fair increased rat, water circulate is troublesome to regulate to ensure that it to be in fixed peak above notch base as a result of the water present is just too excessive.